The luminosity oscillation of X-ray bursters and recurrent novae     

Roberto Aquilano  Mario Castagnino  Luis Lara 《Astrophysics and Space Science》1987,138(1):41-48

Thermo-mechanical oscillations of a radiating spherically-symmetric shell containing a fermion gas (i.e., oscillation where only mechanical, thermodynamical, and eventually radiation phenomena are taken into account) are studied. With a reasonable choice of the three relevant parameters all other observational data are similar to the ones of X-ray bursters and recurrent novae.Therefore, thermo-mechanical oscillations could play an important role in the oscillation spectrum of these astronomical objects.  相似文献   

Functional Molecular Biodiversity: Assessing the Immune Status of Two Sponge Populations (Suberites domuncula) on the Molecular Level     

Heinz C. Schröder  Vladislav A. Grebenjuk  Michael Binder  Alexander Skorokhod  Renato Batel  Hamdy Hassanein  & Werner E. G. Müller 《Marine Ecology》2004,25(2):93-108

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On the petrology and structure of a gravitionally differentiated moon of fission origin     

Alan B. Binder 《Earth, Moon, and Planets》1975,13(4):431-473

In a previous paper, it was shown that the basic properties and the developmental history of a gravitationally differentiated Moon of fission origin match those known for the Moon. In the first part of this report, the models of a differentiated Moon are critically reviewed based on second order considerations of some of the chemical systems used to develope the earlier models and based on new lunar data. As a result, slightly updated models are developed and the results indicate that a Moon of fission origin has a feldspar rich crust (≈70% Or_0.8Ab_5.3An_93.9 with ≈30% pyroxene and olivine) reaching an average depth of ≈65 km. A KREEP rich layer is located at the interface of the crust and the upper mantle. The upper mantle consists of peridotite (≈80% Wo₁₀En₇₀Fs₂₀ and ≈20% Fo_75–80 with ≈3% Al₂O₃ and ≈ 2% TiO₂) and reaches a depth of 300–400 km. Below 300–400 km lies a dunite (≈Fo₉₅) lower mantle. A simple model for the distribution of K, U and Th (and by inference, KREEP) in the differentiated Moon model is developed using a distribution coefficient of 0.1 for the three elements. This coefficient is derived from published data on the distribution of U in Apollo 11 basalts. The simple model successfully accounts for the observed K, U and Th contents of the various mare basalts and upland rocks and yields a heat flow of 21 erg cm^?2s^?1 for the Moon. A model for the fine structure of the peridotite upper mantle of the model Moon is developed based on the TiO₂ and trace element variations observed in the various mare basalts. It is proposed that the upper mantle is rhythmically banded on the scale of 10's of km and that this banding leads to local variations of a factor of ±3 in the K, U and Th content, _-10 ⁺⁵ in the TiO₂ content and _-∞ ⁺² in the olivine content of the peridotite. It is also proposed that this banding leads to large scale horizontal inhomogenuities in the composition of the upper mantle. It is also shown that the formation of the primitive suite of upland rocks is easily explained by the cumulation of plagioclase, which carried varying amounts of pyroxene, olivine and melt with it, during the peritectic crystallization of the last 20% of the differentiating Moon. It is found that the 100 Mg/(Mg+Fe) ratios of the mafics and the An contents of the plagioclases of the rocks are controlled by several factors, the most important of which is the ratio of melt to crystals which together formed the various upland rocks. The inverse relationship between the An contents and the Mg contents of the upland rocks is a direct consequence of the differentiation sequence proposed. The results and models presented in this paper further support the hypothesis that the Moon formed as a result of fission from the proto-Earth.  相似文献   

Spatiotemporal estimation of snow depth using point data from snow stakes,digital terrain models,and satellite data          下载免费PDF全文

Antonio‐Juan Collados‐Lara  Eulogio Pardo‐Igúzquiza  David Pulido‐Velazquez 《水文研究》2017,31(10):1966-1982

Snow availability in Alpine catchments plays an important role in water resources management. In this paper, we propose a method for an optimal estimation of snow depth (areal extension and thickness) in Alpine systems from point data and satellite observations by using significant explanatory variables deduced from a digital terrain model. It is intended to be a parsimonious approach that may complement physical‐based methodologies. Different techniques (multiple regression, multicriteria analysis, and kriging) are integrated to address the following issues: We identify the explanatory variables that could be helpful on the basis of a critical review of the scientific literature. We study the relationship between ground observations and explanatory variables using a systematic procedure for a complete multiple regression analysis. Multiple regression models are calibrated combining all suggested model structures and explanatory variables. We also propose an evaluation of the models (using indices to analyze the goodness of fit) and select the best approaches (models and variables) on the basis of multicriteria analysis. Estimation of the snow depth is performed with the selected regression models. The residual estimation is improved by applying kriging in cases with spatial correlation. The final estimate is obtained by combining regression and kriging results, and constraining the snow domain in accordance with satellite data. The method is illustrated using the case study of the Sierra Nevada mountain range (Southern Spain). A cross‐validation experiment has confirmed the efficiency of the proposed procedure. Finally, although it is not the scope of this work, the snow depth is used to asses a first estimation of snow water equivalent resources.  相似文献   

Implications of measurement metrics on soil freezing curves: A simulation of freeze–thaw hysteresis     

Renato Pardo Lara  Aaron A. Berg  Jon Warland  Gary Parkin 《水文研究》2021,35(7):e14269

Soil freeze–thaw events have important implications for water resources, flood risk, land productivity, and climate change. A property of these phenomena is the relationship between unfrozen water content and sub-freezing temperature, known as the soil freezing characteristic curve (SFC). It is documented that this relationship exhibits hysteretic behaviour when frozen soil thaws, leading to the definition of the soil thawing characteristic curve (STC). Although explanations have been given for SFC/STC hysteresis, the effect that ‘scale’ – particularly ‘measurement scale’ – may have on these curves has received little attention. The most commonly used measurement scale metric is the ‘support’, which is the spatial (or temporal) unit within which the measured variable is integrated or soil volume sampled. We show (a) measurement support can influence the range and shape of the SFC and (b) hysteresis can be attributed, in part, to the support and location of the measurements comprising the SFC/STC. We simulated lab measured temperature, volumetric water content (VWC), and permittivity from soil samples undergoing freeze–thaw transitions using Hydrus-1D and a modified Dobson permittivity model. To assess the effect of measurement support and location on SFC/STC, we masked the simulated temperature and VWC/permittivity extent to match the instrument's support and location. By creating a detailed simulation of the intra- and inter-support variability associated with the penetration of a freezing front, we demonstrate how measurement support and location can influence the temperature range over which water freezing events are captured. We show it is possible to simulate hysteresis in homogenous media with purely geometric considerations, suggesting that SFC/STC hysteresis may be more of an apparent phenomenon than mechanistically real. Lastly, we develop an understanding of how the location and support of soil temperature and VWC/permittivity measurements influence the temperature range over which water freezing events are captured.  相似文献   

Development,urban planning and political decisions. A triad that built territories at risk     

Lara  Alejandro  Bucci  Felipe  Palma  Cristobal  Munizaga  Juan  Montre-Águila  Victor 《Natural Hazards》2021,109(2):1935-1957

Natural Hazards - Chilean geography exposes the country to high-level risks such as earthquakes and tsunamis. The disasters of 1930, 1960, 2010, and 2014 testify to the continuous link between...  相似文献   

Evaluating the effect of land development on sediment transport using a probability density function     

T. V. Hromadka II  R. J. Whitely 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(2):102-108

An important problem in sedimentation analysis is the development of a channel section that preserves, as best as possible, the current sedimentation regime even though the flood frequency tendencies have been altered due to land development within the catchment. In order to accomplish this task, a methodology is needed that estimates sediment transport capacity for various channel configurations. Such a procedure is described which allows the computation of the total sediment transport capacity for each of several T-year return frequency runoff hydrographs. This information is used to obtain an approximate probability distribution for the total sediment transport capacity, and the mean and standard deviation of this distribution are computed.Comparing the results for the catchment in its present state with a future developed state, using a selection of new channel parameters, indicates how to improve the channel to control changes in sedimentation due to development. The analysis procedure provides a basis for estimating a new channel configuration such that the new flow conditions retain, as best as possible, the existing condition sedimentation effects, and hence retain the natural sediment supply and transport trends even though runoff flow rates have changed due to land development within the catchment.The results of Wilson Creek are typical of the several sites examined, see Table 3 below. The T=2, T=5, T=25, and T=100 year values for total sediment transport capacity, in kilotons, are 6.9, 39.4, 61.3, and 96.7 with a mean of 17.1 and standard deviation of 19.3. After development with no change in the channel the respective values increase to: 17.9, 84.6, 128.1, and 258.0 with a mean of 39.1 and standard deviation of 44.3. A new channel can be constructed which will reduce these sediment transport capacity values, after development, to 5.2, 41.0, 62.0, and 124.8 with a mean of 17.4 and standard deviation of 22.0.  相似文献   

An investigation of the Eigenvalue Calibration Method (ECM) using GASP for non-imaging and imaging detectors     

Gillian Kyne  David Lara  Gregg Hallinan  Michael Redfern  Andrew Shearer 《Experimental Astronomy》2016,41(1-2):43-66

Polarised light from astronomical targets can yield a wealth of information about their source radiation mechanisms, and about the geometry of the scattered light regions. Optical observations, of both the linear and circular polarisation components, have been impeded due to non-optimised instrumentation. The need for suitable observing conditions and the availability of luminous targets are also limiting factors. The science motivation of any instrument adds constraints to its operation such as high signal-to-noise (SNR) and detector readout speeds. These factors in particular lead to a wide range of sources that have yet to be observed. The Galway Astronomical Stokes Polarimeter (GASP) has been specifically designed to make observations of these sources. GASP uses division of amplitude polarimeter (DOAP) (Compain and Drevillon Appl. Opt. 37, 5938–5944, 1998) to measure the four components of the Stokes vector (I, Q, U and V) simultaneously, which eliminates the constraints placed upon the need for moving parts during observation, and offers a real-time complete measurement of polarisation. Results from the GASP calibration are presented in this work for both a 1D detector system, and a pixel-by-pixel analysis on a 2D detector system. Following Compain et al. (Appl. Opt. 38, 3490–3502 1999) we use the Eigenvalue Calibration Method (ECM) to measure the polarimetric limitations of the instrument for each of the two systems. Consequently, the ECM is able to compensate for systematic errors introduced by the calibration optics, and it also accounts for all optical elements of the polarimeter in the output. Initial laboratory results of the ECM are presented, using APD detectors, where errors of 0.2 % and 0.1° were measured for the degree of linear polarisation (DOLP) and polarisation angle (PA) respectively. Channel-to-channel image registration is an important aspect of 2-D polarimetry. We present our calibration results of the measured Mueller matrix of each sample, used by the ECM, when 2 Andor iXon Ultra 897 detectors were loaned to the project. A set of Zenith flat-field images were recorded during an observing campaign at the Palomar 200 inch telescope in November 2012. From these we show the polarimetric errors from the spatial polarimetry indicating both the stability and absolute accuracy of GASP.  相似文献   

2-D models of rapidly rotating stars     

F. Espinosa Lara 《Astrophysics and Space Science》2010,328(1-2):291-294

Recent observational advances in the fields of asteroseismology and interferometry, have put in evidence the need of physically realistic models of rapidly rotating stars. In rapidly rotating stars, the centrifugal force affects dramatically the structure of the star and makes it necessary to use 2-D methods that take fully into account the deformation of the star. We compute the structure of rapidly rotating stars using 2-D spectral methods. The advantage of spectral methods compared with finite difference methods is that they can achieve the same accuracy while reducing significantly the number of grid points, thus saving computing time. The models include core convection and realistic microphysics (tabulated equation of state and opacity).  相似文献   

Landslide susceptibility and hazard assessment in San Ramón Ravine, Santiago de Chile, from an engineering geological approach   总被引：1，自引：1，他引：0  

Marisol Lara  Sergio A. Sepúlveda 《Environmental Earth Sciences》2010,60(6):1227-1243

Debris flows and soil and rock slides are among the main geological hazards in the mountain foothills of Central Chile. Geological risk associated with the development of landslides, especially debris flows triggered in the basins of ravines that drain into the capital city, Santiago, has increased in time due to accelerated urban expansion. A landslide hazard evaluation in the San Ramón Ravine, located within the foothills of Santiago is presented. Hazard evaluation is based on a methodology that combines the determination of landslide susceptibility calculated by integration of conditioning factors, with the assessment of slope failure and runout probabilities incorporating geotechnical engineering approaches. The methodology is appropriate for medium or subregional scale studies with limited data. The results show that in San Ramón Ravine the landslide hazard consists mainly of debris flows, rock block slides, rock falls and shallow soil slides. Among these, debris flows are the most important due to the urban area that can be affected. Other case studies show that the method can be used in other regions with minor adaptations for territorial planning or for engineering and environmental purposes.  相似文献